Optical glass with high refractive index

ABSTRACT

An optical glass has a refractive index nd of more than 2.10 and includes at least TiO2, NbO2.5, LaO1.5, SiO2, and B2O3. The glass has the following features: a cation parameter K of 1.8&lt;K≤2.8, wherein K=(Ti-eq.+SiO2+(BO1.5)/2)/(La-eq.), the molar fractions of Ti-eq., SiO2, BO1.5 and La-eq. in the cation parameter K being in cat %; a sum total of glass components SiO2 and B2O3 of 8.0 mol %≤(SiO2+B2O3)≤20.0 mol %, the proportion of B2O3 being &gt;0 mol % and the proportion of SiO2&gt;0 mol %; and a temperature Tmax≤1330° C.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. DE 102022 113 837.2 filed on Jun. 1, 2022, which is incorporated in itsentirety herein by reference. This application also claims priority toGerman Patent Application No. DE 10 2022 101 785.0 filed on Jan. 26,2022, which is incorporated in its entirety herein by reference. Thisapplication also claims priority to German Patent Application No. DE 102021 134 139.6 filed on Dec. 21, 2021, which is incorporated in itsentirety herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to an optical glass, to a glass article and to theuse thereof.

2. Description of the Related Art

The invention concerns glasses that can be used in the optics and lensessectors and also in metaoptics and in “augmented reality” (AR). Thelatter is understood as meaning the augmentation of reality, especiallywith visually presented, computer-generated information. Augmentedreality is realized with the aid of special AR eyeglasses. Inside theseis in each case an optical component comprising one to three planarwaveguides made of glass. The waveguides in turn have integratedgratings, in each case for a wavelength in the red, green or optionallyblue region of the visible spectrum. Via these gratings, the imaginaryimage or information is incoupled/outcoupled in the waveguide to make itvisible to the eye. A high refractive index in the glass substratesserving as waveguides has the advantage that it is possible to achieve awide field of view (FoV). The FoV is here determined by the lowestrefractive index in the system, i.e. by the refractive index of theglass in the red region of the spectrum. Preference is therefore givento glasses that in addition to a high refractive index n_(d) at 587.6 nmalso have a relatively high Abbe number and accordingly low dispersion.Metaoptics are understood as meaning nanooptics on a structural scaleconsiderably smaller—for example by a factor of 5 or a factor of 10—thanthe wavelength of light.

Heavy glass components, i.e. components having a high molar mass, helpincrease the refractive index, also referred to as the refractive power,but at the same time increase the density of glasses, which isdisadvantageous. The density of such glasses here often increasesdisproportionately with increasing refractive index. This means that,even with a possibility of making glass substrates thinner for use inAR, the glass substrate would become heavier, making AR eyeglassesuncomfortable to wear for long periods. Given the trend for headsets tobecome more like standard spectacles in shape, which are then to be wornfor longer or—like normal spectacles—at all times, there is a need forthe eyeglasses to become lighter. Such a reduction on weight is anadvantage for other fields of use too, since camera optics in the DSLRsector are also very often either very bulky or very heavy, which alsosignificantly increases the battery power requirement of the autofocus.

In addition, high-refractive-index glasses optionally have particularlygood internal transmission τ_(i) in the visible wavelength range. In thecase of particularly high-refractive-index glasses, a particular problemin this context has proved to be the internal transmission in the lowervisible wavelength range, for example in the blue region from 420 nm to490 nm, inter alia at 420 nm, 450 nm or 460 nm. Reference is in thiscontext often made to what is known as the “UV edge” of the glass, i.e.the fall in the transmission curve from the visible region of thespectrum to the adjoining UV region. When the UV edge is shifted too farinto the visible region or does not rise steeply enough, thetransmission characteristics in the lower visible wavelength range arenot sufficiently satisfactory for some uses and glasses often have ayellow tinge. Moreover, it has proven difficult to provide glasseshaving a particularly high refractive index across the entire visiblerange (in particular from 380 nm to 800 nm).

A further problem with high-refractive-index glasses is that suchglasses have a high liquidus temperature, i.e. the temperature at whichmelt and solid/crystal are in equilibrium. Below the liquidustemperature, crystals separate out from the melt. Sincehigh-refractive-index glasses have a reduced content of glass formersand very low viscosity, going below the liquidus temperature of suchglasses leads very quickly to the formation of crystals, sincecrystallization is subject to very little kinetic inhibition due to the“thickness” of the melt, or none at all. A high liquidus temperature isaccordingly accompanied by high melting temperatures. A high liquidustemperature is moreover disadvantageous, since at high temperatures aninterfering ingress of refractory material (particularly platinum indissolved and particulate form) can occur. In addition, highertemperatures can result in polyvalent glass components (especiallyniobium and tantalum) undergoing partial reduction and being present ineach case in lower oxidation states, which can lead to the glassacquiring an interfering coloration and to decreased internaltransmission. Low internal transmission distorts the color impression ofa projected image in AR eyeglasses and in other optical components too.A high liquidus temperature also increases the manufacturing costs ofhigh-refractive-index glasses.

Some of the glasses in the prior art derive from the niobium phosphatesystem or titanium phosphate system; they therefore compriseconsiderable proportions of P₂O₅ and niobium and/or titanium. Theseglasses, especially the niobium phosphate glasses, have a refractiveindex of less than 2.1 and are in some cases very problematic inproduction, since loss of oxygen, for example due to excessively highmelting and refining temperatures in a phosphate system that is in anycase already reducing, can result in lower oxidation states. In the caseof niobium, this is for example an oxidation state of less than V and,in the case of titanium, of less than IV. This can result in an intensebrown or even black coloration in the niobium system or in ayellow-green-blue to brown coloration in the titanium system. Inaddition, the titanium in the titanium phosphate system increases thetendency to crystallization significantly, which in the heavy flintsector is a known problem of the existing high-refractive-index glasses,which are then for example no longer re-pressible. Unlike niobium, eventhe highest oxidation state of titanium absorbs at the edge of thevisible range (towards the UV range), which at higher contents givesrise to the known yellow tinge of barium-titanium silicates.

Furthermore, the niobium phosphate family of glasses—like thehigh-refractive-index heavy flint or lanthanum heavy flint family—has atendency not just to interfacial crystallization, but also shows veryrapid crystal growth, which makes post-cooling (tension cooling orsetting the refractive index) critical for optionally preseeded glasses.The glass is moreover known to be relatively brittle and thereforedifficult to polish into very thin wafers.

DE 102006030867 A1 describes optical glasses having a refractive indexn_(d) of 2.000 and higher. The glasses disclosed therein have highcontents of barium oxide, which has an adverse effect on glass formationand on the refractive index.

US 20160194237 A1 describes optical glasses that comprise silicon,boron, lanthanum, titanium, niobium, and zirconium but which generallyhave a refractive index of less than 2.10. EP 3845503A1, JP 2020 59629A1 and WO 2021085271 A1 disclose only glasses having a refractive indexof less than 2.10, in most cases lower even than 2.05.

What is needed in the art is a way to provide optical glasses thatovercome the disadvantages of the prior art. What is also needed in theart is a way to provide glasses that have a high refractive index n_(d)alongside a liquidus temperature that is as low as possible andadvantageously an internal transmission that is as high as possible anda relatively high Abbe number. The glass would advantageously have adensity that is as low as possible, readily undergo heat-forming, and beeasy to work with.

SUMMARY OF THE INVENTION

In some exemplary embodiments provided according to the invention, anoptical glass has a refractive index n_(d) of more than 2.10 andincludes at least TiO₂, NbO_(2.5), LaO_(1.5), SiO₂, and B₂O₃. The glasshas the following features: a cation parameter K of 1.8<K≤2.8, whereinK=(Ti-eq.+SiO₂+(BO_(1.5))/2)/(La-eq.), the molar fractions of Ti-eq.,SiO₂, BO_(1.5) and La-eq. in the cation parameter K being in cat %; asum total of glass components SiO₂ and B₂O₃ of 8.0 mol%≤(SiO₂+B₂O₃)≤20.0 mol %, the proportion of B₂O₃ being >0 mol % and theproportion of SiO₂>0 mol %; and a temperature T_(max)≤1330° C.

In some exemplary embodiments provided according to the invention, aglass article includes an optical glass. The optical glass has arefractive index n_(d) of more than 2.10 and includes at least TiO₂,NbO_(2.5), LaO_(1.5), SiO₂, and B₂O₃. The glass has the followingfeatures: a cation parameter K of 1.8<K≤2.8, whereinK=(Ti-eq.+SiO₂+(BO_(1.5))/2)/(La-eq.), the molar fractions of Ti-eq.,SiO₂, BO_(1.5) and La-eq. in the cation parameter K being in cat %; asum total of glass components SiO₂ and B₂O₃ of 8.0 mol%≤(SiO₂+B₂O₃)≤20.0 mol %, the proportion of B₂O₃ being >0 mol % and theproportion of SiO₂>0 mol %; and a temperature T_(max)≤1330° C. The glassarticle is in the form of a glass substrate, a wafer, a lens, aspherical lens, a prism, an asphere, an optical waveguide, a fibre,and/or a plate

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 illustrates an internal transmission spectrum of exemplary glass31 from Table 1;

FIG. 2 illustrates the relationship of the cation parameter K and Tmaxfor exemplary embodiments and comparative examples from Tables 1 to 9and 14; and

FIG. 3 shows the relationship of the cation parameter K and Tmax forexemplary embodiments and comparative examples from the tables.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

In some embodiments, the invention relates to an optical glass having arefractive index n_(d) of more than 2.10 that comprises at least TiO₂,NbO_(2.5) and LaO_(1.5), the glass having the following features:

-   -   a cation parameter K of 1.8<K≤2.8, where        K=(Ti-eq.+SiO₂+(BO_(1.5))/2)/(La-eq.), the molar fractions of        Ti-eq., SiO₂, BO_(1.5) and La-eq. in the cation parameter K        being in cat %,    -   a sum total of glass components SiO₂ and B₂O₃ of 8.0 mol        %≤(SiO₂+B₂O₃)≤20.0 mol %, the proportion of B₂O₃ being >0 mol %        and the proportion of SiO₂>0 mol %.    -   a temperature T_(max)≤1330° C.

Exemplary embodiments provided according to the invention are based to alarge extent on the correct setting of the molar fractions of cations ofthe glass components with respect to one another. It is thereforeconvenient to characterize the composition of the glass by specifying itin cat %. The glass does also contain anions, in particular oxygen.However, the properties of the glass provided according to the inventionare determined less by the anions, consequently the core of theembodiments provided according to the invention lies more in thecomposition of the cations.

The term “cation-percent” (cat % for short) relates here to the relativemolar fractions of the cations based on the total cation content of theglass. The glass does also contain anions, the relative molar fractionsof which are described in anion-percent (an %) based on the total anioncontent of the glass. In the context of the invention, the cations arein each case specified in the highest oxidation state and showncharge-compensated with oxygen as anion. This does not mean that thecations are necessarily present in glass exclusively in the highestoxidation state. For example, in the case of arsenic and antimony, theremay be cations in the trivalent oxidation state and in the pentavalentoxidation state present side-by-side in the glass. For better clarity,the element name of a composition, for example “niobium”, is also usedin the description of the composition of the glass. This stands in thisinstance for “cations of niobium” and thus does not imply that niobiumis present in elemental form in the glass.

In addition to the cations, the glass provided according to theinvention also includes anions, which are optionally selected from thegroup consisting of O²⁻, F⁻, Br⁻ and Cl⁻. The molar fraction of O²⁻ canoptionally be at least 50% (an %), at least 70%, at least 90%, or atlast 99%, based on the anion content. In some embodiments, the glasscontains only O²⁻ as anion and is free of other anions.

Some compositional features are better described in terms of the molarfraction of the oxidic glass component. In such cases, the individualglass component or the sum total of the glass components is given in mol%. Values in mol % can be calculated from the glass compositionspecified in cat %.

In the context of the invention, a glass system comprising SiO₂ that hasa high TiO₂ content has been found that—unlike the glasses produced fromthe niobium phosphate system or titanium phosphate system that aredescribed in the background—are more stable in respect of the internaltransmission that can be achieved and have a higher refractive index butyet a relatively low density. As the refractive index increases, so doesthe tendency to devitrification. An inventive glass has neverthelessbeen found that has n_(d)>2.10 and is similarly stable in respect ofdevitrification to the known titanium-, niobium- andlanthanum-containing glasses.

An optical glass provided according to the invention has a defined ratioof the proportions (in cat %) of particular cations of the glasscomponents, which is described as the cation parameter K and determinedas follows:

K=(Ti-eq.+SiO₂+(BO_(1.5))/2)/(La-eq.)

For the glasses provided according to the invention, the followingapplies: 1.8<K≤2.8.

This condition describes a composition range within which it is possiblefor the components that are advantageous for achievement of a highrefractive index and high internal transmission to form an amorphousglass, i.e. without the formation of crystal phases. The challenge insuch a high-refractive-index glass system is to obtain a stable glassyregion alongside a low liquidus temperature. The condition according tothe invention has allowed such a composition range to be found, which isdescribed similarly to a miscibility gap in binary or ternary systems.

The glass here also has a temperature T_(max)≤1330° C. and a n_(d) of2.10.

In the cation parameter K, cations of the glass composition areclassified—as published for example in: R. D. Shannon; Revised EffectiveIonic Radii and Systematic Studies of Interatomic Distances in Halidesand Chalcogenides; Acta Crystallographica. Section A 32, 751, 1976—intovarious groups according to their crystal ion radii:

-   -   titanium equivalent (Ti-eq.) is formed from the sum total of the        molar fractions of the cations of titanium (TiO₂), niobium        (NbO_(2.5)), zirconium (ZrO₂), tungsten (WO₃), tantalum        (TaO_(2.5)), aluminum (AlO_(1.5)), antimony (SbO_(2.5)) and        arsenic (AsO_(2.5)), i.e. ions having a relatively small ionic        radius of <100 μm;    -   lanthanum equivalent (La-eq.) is formed from the sum total of        the molar fractions of the cations of lanthanum (LaO_(1.5)),        gadolinium (GdO_(1.5)), yttrium (YO_(1.5)) and ytterbium        (YbO_(1.5)), i.e. ions having a relatively large ionic radius        of >100 pm. La-eq. is the divisor of the cation parameter.

Also included in the condition is the molar cat % of the glass formers(SiO₂) and boron (BO_(1.5)), which are added to the cat % proportion ofthe titanium equivalents and together with Ti-eq. form the dividend ofthe cation parameter. Since it is possible in a glass composition whenconsidering the molar fractions to replace a SiO₂ with a B₂O₃ with therefractive index remaining at about the same level, only half the cat %of BO_(1.5) is included in the condition, i.e. (BO_(1.5))/2.

By selecting and mixing cations of different size in a defined ratio inaccordance with the invention, it is possible to effectively counteractcrystal formation.

The cation parameter K is according to the invention greater than 1.8and max. 2.8. If the cation parameter is 1.8 or less, then T_(max) willbe too high, with the result that internal transmission decreasesthrough the ingress of refractory material and heightened reduction ofpolyvalent oxides brought about by the higher process temperatures thatare necessary. In addition, the refractive index tends to fall when K issmaller, since lanthanum equivalents raise the refractive index lessstrongly than titanium equivalents. However, the cation parameter mustnot be too high either. A K value greater than 2.8 means that the glasscontains too few lanthanum equivalents, which has an adverse effect onthe tendency to crystallization and thus on T_(max). Moreover, if theglass has an excessively high cation parameter K and thus too manytitanium equivalents, it will have a greater tendency to oxidation andthus to discoloration on account of the higher content of polyvalentoxides such as TiO₂ and NbO_(2.5). An advantageous lower limit for thecation parameter may be at least or more than 1.9 or at least 2.0. Someexemplary embodiments have a lower limit for the cation parameter ofmore than 2.0 or a lower limit of at least or more than 2.1 or at leastor more than 2.2 or at least or more than 2.25 or at least or more than2.3. Some embodiments provided according to the invention may have anupper limit for the cation parameter K of at most or less than 2.75 orat most or less than 2.7 or, for some exemplary variants, of at most orless than 2.6.

In addition, in a glass provided according to the invention the sumtotal of the glass components SiO₂ and B₂O₃ is at least 8.0 mol % andnot more than 20.0 mol %, the proportion of B₂O₃ being >0 mol % and theproportion of SiO₂>0 mol %. The proportions of the glass components SiO₂and B₂O₃ in mol % based on oxide can in each case be calculated from thecomposition stated in cat %. A glass provided according to the inventionrequires a sum total (SiO₂+B₂O₃) of at least 8.0 mol %, optionally ofmore than 8.0 mol %, of at least 9.0 mol % or at least 10.0 mol %, inorder for it to be possible for a glassy composition to form in themelting process. However, the sum total should not exceed an upper limitof 20.0 mol %, since otherwise the glass will contain too small aproportion of glass components that increase the refractive index andthe resulting refractive index will thus be too low. An advantageousupper limit for the sum total SiO₂+B₂O₃ may be <20 mol %. For someembodiments, the upper limit of the sum total SiO₂+B₂O₃ may be max. 19.0mol % or max. 18.0 mol %. Some embodiments may also have an upper limitfor the sum total of max. 17.0 mol % or max. 16.5 mol %. B₂O₃ mayoptionally amount to at least 1.0 mol % or at least 1.5 mol % or atleast 2.0 mol % and/or optionally not more than 19.0 mol % or not morethan 17.0 mol % or not more than 15.0 mol % or not more than 13.0 mol %or not more than 12.0 mol %. SiO₂ may optionally amount to at least 1.0mol % or at least 2.0 mol % or at least 3.0 mol % and/or optionally notmore than 19.0 mol % or not more than 18.0 mol % or not more than 16.0mol % or not more than 15.0 mol %.

In addition, the glass provided according to the invention has atemperature T_(max) of ≤1330° C. T_(max) is a composition-dependentglass variable and indicates the temperature that is at least necessaryin the melting process in order to generate a “blank” melt from thestarting materials (for example raw materials, shards, etc.). A “blank”melt is present here when there are no remnants from melting—for exampleincompletely melted raw materials—and no crystals present in the melt.As explained in the introduction, the melting and refining temperaturesshould be as low as possible in order to avoid ingress of refractorymaterial into the glass and coloration of the glass by polyvalent ionsin a low oxidation state. This allows high internal transmission to beachieved. The requirement to achieve the highest-possible internaltransmission means that the chosen melting and refining temperaturescannot be too high, consequently the melting temperature has an upperlimit, hence the use also of the term “T_(max)” for the temperaturedescribed here. T_(max) is thus the lowest temperature at which a blank,crystal-free melt can still be produced. This relationship makes T_(max)a good measure for the liquidus temperature of the glass (see below).

In the context of the invention, the T_(max) of a glass composition isdetermined systematically on a laboratory scale in test series bymelting the same glass from the starting components in small crucibleshaving a volume of in each case 20 ml at different maximum temperatures,with temperature increments of 10° C. chosen. Starting with the lowesttemperature up to the highest temperature, the melting result is thenvisually evaluated in respect of whether a blank melt has been obtainedor whether there are still remnants and/or crystals present in theglass.

The T_(max) value determined for a composition in this way isreproducible even with laboratory melts of larger volume (e.g. 1 litre).Moreover, further experiments have shown that the temperature T_(max) isonly slightly above the liquidus temperature of the glass. It wasinferred that the temperature T_(max), which can be determined in aneasily operated laboratory procedure, is a good measure for the liquidustemperature of the glass, which is not determined exactly here.

In some embodiments, T_(max) is less than 1330° C., for example not morethan 1320° C., optionally not more than 1310° C., optionally not morethan 1300° C. Some embodiments have a T_(max) of not more than 1290° C.or not more than 1280° C.

In addition, a glass provided according to the invention has arefractive index n_(d) of more than 2.10, which makes it possible forthe system, for example a pair of AR eyeglasses, to achieve anadvantageously greater FoV.

In some embodiments, the refractive index n_(d) is more than 2.100,optionally at least 2.110, optionally at least 2.115, optionally atleast 2.120, optionally at least 2.125 or optionally at least 2.130 orat least 2.133. An exemplary upper limit for n_(d) may be 2.20 or 2.200or 2.195 or 2.190 or 2.189. Overall, the refractive index can thus bewithin a range of from 2.10 to 2.20. The refractive index n_(d) is knownto those skilled in the art and refers in particular to the refractiveindex at a wavelength of about 587.6 nm (wavelength of the d line ofhelium). Those skilled in the art will know how the refractive indexn_(d) can be determined.

Optionally, the refractive index is determined with a refractometer, inparticular with a V-block refractometer. In this case, samples having asquare or approximately square base area (for example having dimensionsof about 20 mm×20 mm×5 mm) may in particular be used. In the measurementwith a V-block refractometer, the samples are generally placed in aV-shaped block prism having a known refractive index. The refraction ofan incident light beam depends on the difference between the refractiveindex of the sample and the refractive index of the V-block prism,thereby allowing the refractive index of the sample to be determined.The measurement is optionally carried out at a temperature of 22° C.

In the context of the invention it has been possible to provide anoptical glass having a refractive index n_(d) of more than 2.10 and alow temperature T_(max), that is to say a low liquidus temperature,making it possible to provide a glass having high internal transmission.

An exemplary embodiment provided according to the invention has aninternal transmission of at least 75%, at least 79%, at least 82% or atleast 85% or at least 87% or at least 88% or at least 90% or at least92% or at least 93% or at least 94% or at least 95% or at least 97%,measured at a wavelength of 460 nm and a sample thickness of 10 mm. Whenthe glass is serving as a waveguide, the color impression is notdistorted in the image that is generated in, for example, AR eyeglasses.

The internal transmission or degree of internal transmission can bemeasured using customary methods known to those skilled in the art, forexample according to DIN 5036-1:1978. In this description, stated valuesfor the internal transmission refer to a wavelength of 460 nm and asample thickness of 10 mm. Stating a “sample thickness” does not meanthat the glass has this thickness, but merely states the thickness towhich the stated internal transmission refers.

Unless otherwise stated or obvious to those skilled in the art,measurements described herein are carried out at 20° C. and air pressureof 101.3 kPa.

In some embodiments provided according to the invention, the density ofthe glass is optionally <5.3 g/cm³, optionally <5.2 g/cm³ or <5.1 g/cm³or <5.0 g/cm³.

In some embodiments provided according to the invention, the glasseshave a low density in relation to a high refractive index, which allowsweight savings to be made in optical components, for example in a pairof AR eyeglasses. This can be advantageous when the numerical value forthe ratio (n_(d))²/density is more than 0.85, optionally more than 0.87,optionally more than 0.89, optionally more than 0.90 and/or optionallymore than 0.99, optionally less than 0.98, optionally less than 0.97.

In some embodiments provided according to the invention, the glass hasan Abbe number, i.e. dispersion (ν_(d)), of more than 18.5. Optionally,the dispersion is greater than 18.9, more optionally greater than 19.2and/or more optionally greater than 19.5 and/or less than 30.0 or lessthan 25.0 or less than 24.0. ν_(d) is calculated in known manner, bydetermining the refraction values n_(d) (at about 587.6 nm), n_(F) (atabout 486 nm) and n_(C) (at about 656 nm) using a refractometer andrelating them to one another: v_(d)=(n_(d)−1)/(n_(F)−n_(C)).

In some embodiments, the glass has a glass transition temperature T_(g)of 600° C. to 800° C. Optionally, T_(g) may be more than 670° C., morethan 700° C., optionally more than 720° C. A higher T_(g) can beadvantageous in respect of stability to crystallization since this meansthat the difference in temperature from T_(max) is lower and the glassachieves a stable glassy state more rapidly. The glasses can howeverstill readily undergo heat-forming and processing.

The average coefficient of thermal expansion (CTE) in the 20 to 300° C.temperature range should likewise not be too high, optionally in therange from 8.0 to 12.0 ppm/K, in the range from 8.3 to 11.5 ppm/K,optionally in the range from 8.5 to 11.0 ppm/K. The CTE is determined inaccordance with DIN ISO 7991:1987.

The glass provided according to the invention contains titanium, niobiumand lanthanum. Niobium-containing glasses are reputed to exhibit poorerinternal transmission at the UV end of the visible range of the spectrumand, on account of the titanium content, to have a pronounced tendencyto interfacial crystallization. These disadvantages to not occur withthe lass described herein or occur only to a controllable degree.

Described below are the glass components that form the titaniumequivalents (Ti-eq.) group:

The content of titanium (TiO₂) in the glass may be at least 32.0 cat %,optionally at least 34.0 cat % or at least 35.0 cat %. In someembodiments the content is even at least 37.0 cat % or at least 38.0 cat%. Some embodiments may even contain at least 39 cat % of TiO₂. Thecontent of TiO₂ may optionally be limited to not more than 52.0 cat %,not more than 50.0 cat %, not more than 49.0 cat % or not more than 48.0cat % or not more than 47.0 cat %. In the glasses provided according tothe invention, the component TiO₂ takes on the role of glass formationand can therefore be described as an imperfect glass former. Anexcessively high TiO₂ content would cause a sharp reduction in the Abbenumber.

The proportion of niobium (NbO_(2.5)) in the glass may be at least 3.0cat %, optionally at least 4.0 cat %, optionally at least 4.5 cat %,optionally at least 5.0 cat % or at least 6.0 cat %. The content ofNbO_(2.5) may optionally be limited to not more than 15.0 cat %, notmore than 13.0 cat %, not more than 11.0 cat % or not more than 10.0 cat%. Some embodiments may even contain max. 9.0 cat %. Alongside TiO₂ andLaO_(1.5), NbO_(2.5) contributes to a high refractive index. However,excessively high NbO_(2.5) contents are disadvantageous in this glasssystem and result in increased crystallization.

The proportion of zirconium (ZrO₂) in the glass may be 0 to 11.0 cat %.There may be present in the glass at least 1.0 cat % or at least 2.0 cat%, optionally at least 3.0 cat % or at least 4.0 cat %, of ZrO₂. ZrO₂can contribute to setting the cation parameter such that a glassy regionwith correspondingly low T_(max) is achieved for the glass system. Thecontent of ZrO₂ may optionally be limited to not more than 11.0 cat %,not more than 10.0 cat %, not more than 9.0 cat % or not more than 8.0cat %. Some embodiments may even contain max. 7.0 cat %. ZrO₂contributes to achieving the high refractive index, but at high amountsit also increases the tendency of the glass to crystallization,consequently its content is optionally limited. ZrO₂-free variants arepossible.

Tungsten (WO₃) is an optional component of the glass. WO₃ may be presentin the glass in a content of max. 5.0 cat %, optionally max. 3.0 cat %,optionally max. 2 cat % or max. 1.5 cat % or max. 1 cat % or max. 0.7cat %. When this component is present, a lower limit may be 0.1 cat %,optionally 0.3 cat %. WO₃-free variants are possible and advantageous.

Tantalum (TaO_(2.5)) is an optional component of the glass. TaO_(2.5)may be present in the glass in a content of max. 5.0 cat %, optionallymax. 3.0 cat %, optionally max. 2.0 cat % or max. 1.0 cat % or max. 0.7cat %. When this component is present, a lower limit may be 0.1 cat %,optionally 0.3 cat %. TaO_(2.5)-free variants are also possible and maybe advantageous.

Aluminum (AlO_(1.5)) is an optional component of the glass that cancontribute to the chemical resistance, but also to the refractive indexof the glass. Its content may be from 0 to 5.0 cat % or up to 3.0 cat %or up to 2.0 cat % or up to 1.0 cat %. When AlO_(1.5) is present, it maybe present in a proportion of at least 0.1 cat % or at least 0.5 cat %.Some embodiments are free of AlO_(1.5).

Antimony (SbO_(2.5)) and arsenic (AsO_(2.5)) are optional components andmay be present in the glass in each case and independently of oneanother in a content of max. 0.5 cat %, optionally max. 0.3 cat % ormax. 0.1 cat % or max. 0.05 cat %. When at least one of these componentsis present in the glass, 0.005 cat % may be a lower limit in each case.SbO_(2.5)- and/or AsO_(2.5)-free variants are possible. Since the meltsof the glasses provided according to the invention have low thickness,the use of classical refining agents to reduce bubble formation can bedispensed with. Vacuum refining may optionally be employed. SbO_(2.5)and/or AsO_(2.5) may however be added to the mixture in order to keepthe glass melt in an oxidizing state at high melting and refiningtemperatures so that polyvalent ions, especially titanium and niobiumions, are not present in their respective lower oxidation states, withthe result that the internal transmission of the glass produced isimproved.

It may be advantageous when the total proportion of titanium equivalents(Ti-eq.) in the glass, i.e. the sum total ofTiO₂+NbO_(2.5)+ZrO₂+WO₃+AlO_(1.5)+TaO_(2.5)+AsO_(2.5)+SbO_(2.5), is atleast 43.0 cat % or at least 44.0 cat %. In some embodiments, the sumtotal may be at least 45.0 cat % or at least 46.0 cat %, optionally atleast 47.0 cat %, optionally at least 49.0 cat % or at least 50.0 cat %and/or not more than 63.0 cat %, optionally not more than 61.0%,optionally not more than 59.0% or not more than 58.0%. An excessivelyhigh amount of titanium equivalent can result in crystallization and ahigh T_(max). The same applies to an excessively low amount.

In some embodiments provided according to the invention, the featuretitanium equivalent is formed from the sum total of the molar fractionsof the cations of titanium (TiO₂), niobium (NbO_(2.5)), zirconium(ZrO₂), antimony (SbO_(2.5)) and arsenic (AsO_(2.5)), with the upperlimits and/or lower limits stated above for the total proportion oftitanium equivalents (Ti-eq.) accordingly applying. It is self-evidentthat the glasses in such embodiments are essentially free of WO₃,AlO_(1.5) and TaO_(2.5).

In some embodiments, the feature titanium equivalent is formed from thesum total of the molar fractions of the cations of titanium (TiO₂),niobium (NbO_(2.5)) and zirconium (ZrO₂), with the upper limits and/orlower limits stated above for the total proportion of titaniumequivalents (Ti-eq.) accordingly applying. It is self-evident that theglasses in such embodiments are essentially free of WO₃, AlO_(1.5),TaO_(2.5), AsO_(2.5) and SbO_(2.5).

In some embodiments, the following condition is satisfied: content ofTiO₂ (in cat %) >content of NbO_(2.5) (in cat %)>content of ZrO₂ (in cat%).

Described below are the glass components forming the lanthanumequivalents (La-eq.) group:

The content of lanthanum (LaO_(1.5)) in the glass may be at least 13.0cat %, optionally at least 15.0 cat % or at least 16.0 cat %. In someembodiments the content is even at least 17.0 cat % or at least 18.0 cat%. In some embodiments the content is even at least 19.0 cat % or atleast 20 cat %. The content of LaO_(1.5) may optionally be limited tonot more than 30.0 cat % or not more than 29.0 cat %. Some embodimentsmay have a LaO_(1.5) content of not more than 28.0 cat %, not more than26.0 cat %, not more than 25.0 cat % or not more than 24.0 cat % or notmore than 23.0 cat %. Alongside TiO₂ and NbO_(2.5), LaO_(1.5)contributes to a high refractive index. Excessively high contents ofLaO_(1.5) contribute to increased devitrification and thus to anincrease in T_(max).

The proportion of gadolinium (GdO_(1.5)) in the glass may be 0 to 10.0cat %. When it is present, the proportion may be at least 1.0 cat %,optionally at least 2.0 cat % or at least 3.0 cat %. The content ofGdO_(1.5) may optionally be limited to not more than 10.0 cat %, notmore than 9.0 cat %, not more than 8.0 cat % or not more than 7.0 cat %.Some embodiments may also contain max. 6.0 cat % or max. 5.0 cat % ofGdO_(1.5).

Yttrium (YO_(1.5)) is an optional component of the glass and may bepresent in the glass in a content of max. 5.0 cat %, optionally max. 3.0cat %, optionally max. 2.0 cat % or max. 1.5 cat % or max. 1.0 cat %.When this component is present, a lower limit may be 0.1 cat %,optionally 0.3 cat %. YO_(1.5)-free variants are possible.

Ytterbium (YbO_(1.5)) is an optional component of the glass and may bepresent in the glass in a content of max. 5.0 cat %, optionally max. 3.0cat %, optionally max. 2 cat % or max. 1.5 cat % or max. 1.0 cat %. Whenthis component is present, a lower limit is advantageously 0.1 cat %,optionally 0.3 cat %. YO_(1.5)-free variants are possible and may beadvantageous.

It may be advantageous when the total proportion of lanthanumequivalents (La-eq.) in the glass, i.e. the sum totalLaO_(1.5)+GdO_(1.5)+YO_(1.5)+YbO_(1.5) in the glass is at least 21.0 cat%, optionally at least 22.0 cat %, optionally at least 23.0 cat % or atleast 24.0 cat % and/or not more than 35.0 cat %, not more than 33.0 cat%, not more than 31.0 cat %. Some embodiments may also contain not morethan 30.0 cat %, optionally not more than 29.0 cat %, optionally notmore than 28.0 cat % or, in some embodiments, not more than 27.0 cat %,of lanthanum equivalents. An excessively high amount of lanthanumequivalent can result in crystallization and a high T_(max). The sameapplies to an excessively low amount.

In some embodiments, the feature lanthanum equivalent is formed from thesum total of the molar fractions of the cations of lanthanum(LaO_(1.5)), gadolinium (GdO_(1.5)) and yttrium (YO_(1.5)), with theupper limits and/or lower limits stated above for the total proportionof lanthanum equivalents (La-eq.) accordingly applying. It isself-evident that the glasses in such embodiments are essentially freeof YbO_(1.5).

In some embodiments, the following condition is satisfied: content ofLaO_(1.5) (in cat %)>content of GdO_(1.5) (in cat %)>content of YO_(1.5)(in cat %).

In some embodiments, the proportion of the components TiO₂ and LaO_(1.5)in the glass is at least 53.0 cat %, optionally at least 55.0 cat %,optionally at least 57.0 cat %, optionally at least 59.0 cat % and/ornot more than 70.0 cat %, optionally not more than 69.0 cat % or notmore than 68 cat %.

In some embodiments, the proportion of the components TiO₂, LaO_(1.5)and NbO_(2.5) is at least 60.0 cat %, optionally at least 63.0 cat %,optionally at least 65.0 cat %, optionally at least 67.0 cat % and/ornot more than 80.0 cat %, optionally not more than 77 cat % or not morethan 75 cat %, optionally not more than 73.0 cat %.

For the optical glass it may be advantageous when the sum total(Ti-eq.+La-eq.) in the glass is at least 72.0 cat %, optionally at least73.0 cat %, optionally at least 74.0 cat % and/or not more than 85.0 cat%, optionally not more than 84.0 cat %, optionally not more than 83.0cat %. Some embodiments also have a lower limit for the sum total(Ti-eq.+La-eq.) of at least 75.0 cat % or at least 76.0 cat %. Thehigher the sum total, the higher the refractive index of the glass.However, as the sum total increases, so it also becomes more difficultto provide a glass that is stable to crystallization and has a highT_(max) and accordingly high internal transmission.

Silicon (SiO₂) is a glass former. The component contributes to thechemical resistance. If it is used in very large amounts, the refractiveindex values of the invention cannot be achieved. According to theinvention, the glass contains SiO₂ in a proportion of >0 cat %.Optionally, the glass contains at least 1.0 cat %, at least 2.0 cat % orat least 3.0 cat %. Some embodiments may also contain at least 4.0 cat %or at least 5.0 cat % of SiO₂. The SiO₂ content may be limited to lessthan 20.0 cat %, max. 18.0 cat % or max. 16.0 cat % or max. 14.0 cat %or max. 13.0 cat % or max. 12.0 cat %.

Boron (BO_(1.5)) likewise acts as a glass former. In the glass systemprovided according to the invention it contributes to the lowering oftemperature T_(max). According to the invention, the glass containsBO_(1.5) in a proportion of >0 cat %. Optionally, the glass contains atleast 1.0 cat %, at least 2.0 cat % or at least 3.0 cat %. Someembodiments may also contain at least 4.0 cat % or at least 5.0 cat % orat least 6.0 cat % of BO_(1.5). The BO_(1.5) content may be limited toless than 20.0 cat %, max. 19.0 cat % or max. 18.0 cat %. Someembodiments contain BO_(1.5) in a proportion of max. 17.0 cat % or max.16.0 cat % or max. 14.0 cat % or max. 12.0 cat % or max. 11.0 cat %.

With respect to the proportions of the components SiO₂ and BO_(1.5), itshould be noted that the proportions are to be selected such that thecondition of 8.0 mol %≤(SiO₂+B₂O₃)≤20.0 mol % is satisfied. Furtherexemplary upper limits and lower limits for this feature have alreadybeen stated hereinabove.

The glass may comprise barium (BaO). The content of BaO is in someembodiments restricted to not more than 6.5 cat %, not more than 6.0 cat%, in some embodiments to not more than 5.5 cat %, since excessivelyhigh proportions result in undesired crystallization. When BaO ispresent in the glass, this component may amount to at least 0.1 cat %,at least 0.2 cat %, at least 0.5 cat %, or at least 1.0 cat %, at least2.0 cat % or at least 3.0 cat %. The presence of BaO in the glass can behelpful in ensuring the viscosity is higher and steeper in thehigh-viscosity range from approx. 10⁶ dPas to 10¹⁴ dPas. BaO-freevariants are possible.

Zinc (ZnO), magnesium (MgO), calcium (CaO) and/or strontium (SrO) mayoptionally be used in the glass. They lower the melting temperature andstabilize the glass against crystallization without reducing itschemical resistance to the degree brought about by alkali metal oxides.The content of ZnO may here be from 0 to 5.0 cat %, up to max. 4.0 cat %or up to max. 3.0 cat % or up to max. 2.0 cat % or up to max. 1.0 cat %.Some embodiments are free of ZnO. The content of MgO may be from 0 to2.0 cat % or up to max. 1.0 cat %. Some embodiments are free of MgO. Thecontent of CaO may be from 0 to 2.0 cat % or up to max. 1.0 cat %. Someembodiments are free of CaO. The content of SrO may be from 0 to 2.0 cat% or up to max. 1.0 cat %. Some embodiments are free of SrO. For thecomponents mentioned, an exemplary lower limit may in each case be atleast 0.1 cat % or at least 0.3 cat % or at least 0.5 cat %.

Alkali metal oxides, such as LiO_(0.5), NaO_(0.5), KO_(0.5), RbO_(0.5),CsO_(0.5), may be present in the glass in a proportion for theindividual components, in a proportion for the sum total thereof, ofmax. 2 cat %, max. 1 cat %, optionally max. 0.5 cat %. Small amounts ofat least 0.1 cat % or at least 0.2 cat % (for the individual componentsor optionally for the sum total thereof) may be advantageous for themeltability of the glass. However, since these components lower therefractive index, there is an upper limit on the content thereof. Someembodiments are free of LiO_(0.5) and/or NaO_(0.5) and/or KO_(0.5)and/or RbO_(0.5) and/or CsO_(0.5), optionally free of alkali metaloxides.

Tin oxide (SnO₂) shows only very low or no activity as a refining agentin the glass system provided according to the invention. It may howeverbe present as a glass component in a proportion of max. 2 cat % or max.1 cat % or max. 0.5 cat %. Optionally, the glass is SnO₂-free.

Sulfate (SO₃) may be present in a small proportion in the glass in orderto stabilize higher oxidation states in polyvalent ions. When it ispresent, the proportion is at least 0.01 cat %. Higher proportions ofsulfate increase the risk of pronounced bubble formation in the glassand the risk of platinum getting into the glass. The sulfate content maytherefore be max. 0.5 cat %, optionally max. 0.1 cat %, optionally max.0.05 cat %. Optionally, the glass is SO₃-free.

The glass may contain small amounts of hafnium (HfO₂), optionally max.0.1 cat % or max. 0.05 cat %. It is generally not actively added butgets into the glass with the component ZrO₂ via the raw material. Ifusing very pure ZrO₂ raw material, the glass may be HfO₂-free.

The optical glass may comprise fluorine (F). Embodiments may containmax. 1 cat %, optionally max. 0.5 cat %, optionally max. 0.1 cat %, ofthis component. Some embodiments are free of F.

In some embodiments, the glass includes the following components in cat%:

SiO₂   >0 to <20.0 BO_(1.5)   >0 to <20.0 TiO₂ 32.0 to 52.0 NbO_(2.5) 3.0 to 15.0 ZrO₂   0 to 11.0 WO₃   0 to 5.0 TaO_(2.5)   0 to 5.0AlO_(1.5)   0 to 5.0 SbO_(2.5)   0 to 0.5 AsO_(2.5)   0 to 0.5 LaO_(1.5)13.0 to 30.0 GdO_(1.5)   0 to 10.0 YO_(1.5)   0 to 5.0 YbO_(1.5)   0 to5.0

In some embodiments, the glass includes the following components in cat%:

SiO₂   >0 to <20.0 BO_(1.5)   >0 to <20.0 TiO₂ 32.0 to 52.0 NbO_(2.5) 4.0 to 15.0 ZrO₂   0 to 11.0 WO₃   0 to 5.0 TaO_(2.5)   0 to 5.0AlO_(1.5)   0 to 5.0 SbO_(2.5)   0 to 0.5 AsO_(2.5)   0 to 0.5 LaO_(1.5)13.0 to 28.0 GdO_(1.5)   0 to 10.0 YO_(1.5)   0 to 5.0 YbO_(1.5)   0 to5.0

In some embodiments, the glass includes the following components in cat%:

SiO₂  2.0 to 14.0 BO_(1.5)  1.0 to 18.0 TiO₂ 34.0 to 50.0 NbO_(2.5)  5.0to 13.0 ZrO₂ 2.0 to 8.0 WO₃   0 to 2.0 TaO_(2.5)   0 to 1.0 AlO_(1.5)  0 to 2.0 SbO_(2.5)   0 to 0.1 AsO_(2.5)   0 to 0.1 LaO_(1.5) 16.0 to24.0 GdO_(1.5) 2.0 to 8.0 YO_(1.5) 0.3 to 2.0 BaO   0 to 6.5

In some embodiments the glass consists to an extent of at least 95.0 cat%, of at least 98.0 cat % or of at least 99.0 cat %, of the componentsdescribed herein, especially of the components listed in the tablesabove. In some embodiments the glass essentially consists entirely ofthese components.

As already explained above, the addition of classical refining agents isnot necessary, since the melt has low thickness at the temperaturesnecessary for melting. When refining agents such as AsO_(2.5),SbO_(2.5), SO₃ and/or Cl are nevertheless added, the content thereof canbe significantly lowered, for example to <0.1 cat %. Pure physicalrefinement is moreover possible and may be advantageous. The glass mayoptionally include one or more of the following components having arefining effect in the stated proportions in cat %.

SbO_(2.5) 0.0 to 0.5 AsO_(2.5) 0.0 to 0.5 SO₃ 0.0 to 0.5 Cl 0.0 to 0.5

In some embodiments the glass is essentially free of cations of bismuth(BiG_(1.5)) and/or lead (PbO). The addition of bismuth would increasethe density of the glass disproportionately. Moreover, bismuth ionsundergo reduction to elemental bismuth even at relatively lowtemperatures in the region of 1000° C., imparting a strong greycoloration to the glass. PbO is likewise avoided because of its adverseeffect on a low density. It is also one of the toxic components.

The high contents of niobium, titanium and lanthanum means that costlycomponents such as tantalum and/or tungsten and/or ytterbium and/orgermanium (GeO₂) are not necessary in the glass, or necessary only insmall proportions, in order to obtain a glass having the desired highrefractive index. Lithium is known for its aggressiveness towardsceramic bath and crucible materials and is therefore also where possiblenot used, or used only in small amounts.

Optionally, the glass is free of phosphate (PO_(2.5)), since this makesthe melt significantly reducing and thus significantly increases theoxygen requirement of the melt, which in turn increases platinumconsumption, resulting in coloration of the glass.

Optionally, the glass is—based on the respective cations—essentiallyfree of one or more constituents selected from magnesium, cadmium,gallium, germanium, coloring components—for example cobalt, vanadium,chromium, molybdenum, copper, nickel—and combinations thereof.Components such as iron, manganese, selenium, tellurium and/or thalliummay be present in small proportions in the glass, for example they mayget into the glass as impurities. Particularly iron, selenium andtellurium, but also manganese can act as redox partners. It may howeverbe advantageous when these components too are not specifically added tothe glass either individually or in combination

When this description states that the glass is free of a component ordoes not contain a certain component, what this means is that saidcomponent may at most be present as an impurity in the glass. This meansthat it is not added in significant amounts. Not significant amounts areamounts according to the invention of less than 100 ppm, optionally lessthan 50 ppm or less than 10 ppm (m/m).

In some embodiments, the invention relates to a glass article thatincludes or consists of the described glass. The glass article can takedifferent forms. Optionally, the article has the form

-   -   of a glass substrate, especially as a constituent of a stack of        substrates for an optical component, especially in a pair of AR        eyeglasses,    -   a wafer, especially having a maximum diameter of 5.0 cm to 50.0        cm or having a diameter between 0.7 cm and 50 cm, optionally        between 3 cm and 45 cm, or between 5 cm and 40 cm,    -   a lens, especially a spherical lens, a prism or an asphere,        and/or    -   an optical waveguide, especially a fibre or plate.

In a further aspect the invention relates to the use of a glass or glassarticle described herein in AR eyeglasses, metaoptics, wafer-leveloptics, optical wafer applications or classical optics. Alternatively orin addition, the glass or glass article described herein may be used asa wafer, lens, spherical lens or optical waveguide.

The glasses provided according to the invention may be produced bymelting commercial raw materials. For example, it is possible to meltthe glasses in a device as described in the as yet unpublished DE102020120168.

Examples

The compositions shown in Tables 1 to 14 that follow were melted andtheir properties investigated: Tables 1 to 13 show exemplary embodimentsprovided according to the invention (examples 1 to 99) and Table 14comparative examples (comparative examples A to G). In some of theglasses the internal transmission was determined. The internaltransmission of example 31 is shown in FIG. 1 .

Compositions and Properties

TABLE 1 Cat % 1 2 3 4 5 6 7 8 AlO_(1.5) BO_(1.5) 11.88 11.88 11.88 17.3513.95 10.43 6.76 2.96 BaO 3.75 4.95 4.95 4.92 5.01 5.11 5.21 5.31 CaOGdO_(1.5) 3.28 3.13 6.26 3.00 3.06 3.12 3.18 3.24 KO_(0.5) LaO_(1.5)22.97 21.92 18.79 21.02 21.42 21.82 22.24 22.68 NbO_(2.5) 6.41 6.41 6.416.01 6.12 6.23 6.35 6.48 SiO₂ 4.75 4.75 4.75 3.65 5.58 7.58 9.66 11.82SrO TiO₂ 42.70 42.70 42.70 40.04 40.78 41.55 42.36 43.19 YO_(1.5) ZnOZrO₂ 4.27 4.27 4.27 4.00 4.08 4.16 4.24 4.32 WO₃ TaO_(2.5) SbO_(2.5)AsO_(2.5) Cation 2.44 2.56 2.56 2.60 2.60 2.60 2.60 2.60 parameter B₂O₃7.64 7.58 7.58 11.37 8.98 6.58 4.19 1.80 [mol %] SiO₂ [mol %] 6.11 6.066.06 4.79 7.18 9.57 11.97 14.36 SiO₂ + B₂O₃ 13.75 13.64 13.64 16.1616.16 16.15 16.16 16.16 [mol %] Properties T_(max) [° C.] 1280 1280 13001300 1300 1300 1300 1320 n_(d) 2.161 2.156 2.153 2.135 2.137 2.139 2.1412.143 v_(d) 20.4 20.5 20.3 20.8 20.8 20.8 20.8 20.9 Density 4.98 4.964.94 4.90 4.91 4.94 4.94 4.96 [g/cm³] n_(d) ²/Density 0.937 0.936 0.9390.931 0.930 0.927 0.927 0.926

TABLE 2 Cat % 9 10 11 12 13 14 15 16 AlO_(1.5) 0.61 BO_(1.5) 10.43 10.4310.43 10.43 10.43 10.43 10.43 10.43 BaO 4.95 5.16 5.16 4.64 4.64 5.165.16 5.16 CaO 0.52 GdO_(1.5) 3.02 3.15 3.15 3.15 3.15 3.15 3.15 3.15KO_(0.5) LaO_(1.5) 21.13 22.03 22.03 22.03 22.03 21.02 22.03 22.03NbO_(2.5) 6.35 6.20 6.20 6.20 6.20 6.20 6.20 10.33 SiO₂ 7.58 7.58 6.987.58 7.58 7.58 7.58 7.58 SrO 0.52 TiO₂ 42.31 41.33 41.33 41.33 41.3341.33 40.29 37.19 YO_(1.5) 1.01 ZnO 1.03 ZrO₂ 4.23 4.13 4.13 4.13 4.134.13 4.13 4.13 WO₃ TaO_(2.5) SbO_(2.5) AsO_(2.5) Cation 2.72 2.56 2.562.56 2.56 2.56 2.52 2.56 parameter B₂O₃ 6.55 6.59 6.62 6.59 6.59 6.596.59 6.77 [mol %] SiO₂ [mol %] 9.53 9.59 8.85 9.59 9.59 9.59 9.59 9.84SiO₂ + B₂O₃ 16.08 16.18 15.47 16.18 16.18 16.18 16.18 16.61 [mol %]Properties T_(max) [° C.] 1320 1280 1280 1280 1280 1280 1280 1280 n_(d)2.143 2.138 2.137 2.136 2.139 2.139 2.133 2.135 v_(d) 20.6 20.9 20.920.9 20.8 20.9 21.1 21.1 Density 4.90 4.93 4.94 4.94 4.93 4.93 4.96 4.96[g/cm³] n_(d) ²/Density 0.937 0.926 0.925 0.924 0.929 0.928 0.916 0.918

TABLE 3 Cat % 17 18 19 20 21 22 23 24 AlO_(1.5) BO_(1.5) 10.43 10.436.76 10.43 10.43 10.43 9.52 9.52 BaO 5.16 5.16 5.26 5.19 5.16 5.19 5.315.23 CaO GdO_(1.5) 3.15 3.15 3.21 3.17 3.15 3.17 3.24 3.19 KO_(0.5)LaO_(1.5) 22.03 21.02 21.43 21.15 21.02 21.15 21.91 21.57 NbO_(2.5) 6.206.20 6.32 6.18 6.20 6.18 6.42 6.48 SiO₂ 7.58 7.58 9.66 7.58 7.58 7.585.71 5.71 SrO TiO₂ 38.74 40.29 41.07 41.18 40.81 40.66 42.82 43.20YO_(1.5) 1.01 1.03 1.01 1.01 1.01 0.78 0.77 ZnO 1.03 1.05 0.52 0.51 ZrO₂6.72 4.13 4.21 4.12 4.13 4.12 4.28 4.32 WO₃ TaO_(2.5) SbO_(2.5)AsO_(2.5) Cation 2.56 2.52 2.52 2.54 2.54 2.52 2.47 2.53 parameter B₂O₃6.59 6.59 4.19 6.60 6.59 6.60 6.02 6.01 [mol %] SiO₂ [mol %] 9.59 9.5911.98 9.59 9.59 9.59 7.23 7.21 SiO₂ + B₂O₃ 16.18 16.18 16.17 16.19 16.1816.19 13.25 13.22 [mol %] Properties T_(max) [° C.] 1280 1300 1320 13001300 1300 1280 1290 n_(d) 2.129 2.134 2.136 2.138 2.136 2.136 2.1572.158 v_(d) 21.5 21.1 21.1 20.9 21.0 21.0 20.6 20.5 Density 4.98 4.944.96 4.92 4.93 4.94 4.98 4.98 [g/cm³] n_(d) ²/Density 0.911 0.922 0.9210.930 0.927 0.923 0.934 0.935

TABLE 4 Cat % 25 26 27 28 29 30 31 32 AlO_(1.5) BO_(1.5) 9.52 9.52 7.417.41 7.41 7.41 10.43 10.43 BaO 5.15 5.07 5.37 5.29 5.21 5.12 5.16 5.19CaO GdO_(1.5) 3.14 3.09 3.28 3.23 3.18 3.13 3.15 3.17 KO_(0.5) LaO_(1.5)21.24 20.91 22.15 21.81 21.48 21.14 21.27 21.41 NbO_(2.5) 6.54 6.59 6.786.84 6.90 6.96 6.20 6.18 SiO₂ 5.71 5.71 4.48 4.48 4.48 4.48 7.58 7.58SrO TiO₂ 43.58 43.96 45.22 45.60 45.99 46.37 40.81 40.66 YO_(1.5) 0.750.74 0.79 0.77 0.76 0.75 0.76 0.76 ZnO 0.52 0.51 ZrO₂ 4.36 4.40 4.524.56 4.60 4.64 4.13 4.12 WO₃ TaO_(2.5) SbO_(2.5) AsO_(2.5) 0.01 0.01Cation 2.58 2.64 2.47 2.53 2.58 2.64 2.54 2.52 parameter B₂O₃ 6.00 5.984.65 4.64 4.63 4.62 6.59 6.60 [mol %] SiO₂ [mol %] 7.20 7.18 5.61 5.605.59 5.58 9.59 9.59 SiO₂ + B₂O₃ 13.20 13.16 10.26 10.24 10.22 10.2016.18 16.19 [mol %] Properties T_(max) [° C.] 1300 1290 1320 1310 13101290 1280 1280 n_(d) 2.160 2.162 2.178 2.181 2.182 2.184 2.136 2.135v_(d) 20.4 20.3 20.1 20.0 19.9 19.8 21.0 21.0 Density 4.96 4.94 5.035.02 5.01 4.99 4.94 4.94 [g/cm³] n_(d) ²/Density 0.942 0.946 0.943 0.9480.951 0.955 0.924 0.924

TABLE 5 Cat % 33 34 35 36 37 38 39 40 AlO_(1.5) BO_(1.5) 10.43 10.4310.43 10.43 10.43 10.43 10.43 9.52 BaO 5.11 5.16 5.16 4.64 4.64 4.645.16 5.18 CaO 0.52 GdO_(1.5) 3.12 3.15 3.15 3.15 3.15 3.15 3.15 3.16KO_(0.5) 0.52 LaO_(1.5) 21.07 21.27 21.27 21.27 21.27 21.27 21.27 21.37NbO_(2.5) 6.23 6.20 6.20 6.20 6.20 6.20 6.20 6.23 SiO₂ 7.58 7.58 7.587.58 7.58 7.58 7.58 8.10 SrO 0.52 TiO₂ 41.04 40.81 40.29 40.81 40.8140.81 40.29 41.00 YO_(1.5) 0.75 0.76 0.76 0.76 0.76 0.76 0.76 0.76 ZnO0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 ZrO₂ 4.16 4.13 4.13 4.13 4.134.13 4.13 4.15 WO₃ 0.52 TaO_(2.5) 0.52 SbO_(2.5) AsO_(2.5) 0.01 Cation2.58 2.54 2.54 2.54 2.54 2.54 2.54 2.54 parameter B₂O₃ 6.58 6.59 6.596.59 6.59 6.61 6.61 5.99 [mol %] SiO₂ [mol %] 9.57 9.59 9.59 9.59 9.599.62 9.62 10.19 SiO₂ + B₂O₃ 16.15 16.18 16.18 16.18 16.18 16.23 16.2316.18 [mol %] Properties T_(max) [° C.] 1280 1300 1300 1300 1300 13001300 1300 n_(d) 2.137 2.136 2.135 2.135 2.138 2.135 2.136 2.137 v_(d)20.9 21.0 20.9 21.0 20.9 21.0 21.0 21.0 Density 4.92 4.94 4.95 4.93 4.934.90 4.97 4.94 [g/cm³] n_(d) ²/Density 0.928 0.923 0.921 0.923 0.9280.929 0.918 0.925

TABLE 6 Cat % 41 42 43 44 45 46 47 48 AlO_(1.5) BO_(1.5) 11.32 11.3211.32 7.69 9.52 10.43 8.61 8.61 BaO 5.13 5.26 5.18 5.28 5.18 4.64 5.275.19 CaO 0.52 GdO_(1.5) 3.13 3.21 3.16 3.22 3.40 3.15 3.22 3.17 KO_(0.5)LaO_(1.5) 21.17 21.70 21.37 21.78 22.98 21.27 21.75 21.41 NbO_(2.5) 6.176.36 6.42 6.54 6.06 6.20 6.79 6.84 SiO₂ 7.08 4.72 4.72 6.73 7.62 7.583.83 3.83 SrO TiO₂ 40.62 42.42 42.79 43.62 39.88 39.78 44.68 45.06YO_(1.5) 0.75 0.77 0.76 0.77 0.82 0.76 0.77 0.76 ZnO 0.51 0.50 0.52 0.570.57 ZrO₂ 4.11 4.24 4.28 4.36 4.04 4.13 4.52 4.56 WO₃ 0.52 TaO_(2.5)0.52 SbO_(2.5) AsO_(2.5) 0.01 Cation 2.54 2.47 2.53 2.53 2.29 2.54 2.492.55 parameter B₂O₃ 7.19 7.23 7.21 4.81 6.06 6.61 5.42 5.41 [mol %] SiO₂[mol %] 8.99 6.02 6.01 8.41 9.69 9.62 4.82 4.81 SiO₂ + B₂O₃ 16.18 13.2513.22 13.22 15.75 16.23 10.24 10.22 [mol %] Properties T_(max) [° C.]1300 1300 1310 1310 1320 1320 1320 1320 n_(d) 2.136 2.156 2.157 2.1602.134 2.136 2.177 2.178 v_(d) 21.0 20.6 20.5 20.5 21.4 20.8 20.1 20.0Density 4.93 4.97 4.96 4.98 5.00 4.92 5.03 5.02 [g/cm³] n_(d) ²/Density0.925 0.934 0.938 0.937 0.912 0.927 0.941 0.945

TABLE 7 Cat % 49 50 51 52 53 54 55 56 AlO_(1.5) BO_(1.5) 8.61 8.61 8.6110.43 10.43 10.43 10.43 10.43 BaO 5.11 5.03 4.95 5.01 4.90 5.12 5.085.03 CaO GdO_(1.5) 3.12 3.07 3.02 3.06 2.99 3.13 3.10 3.07 KO_(0.5)LaO_(1.5) 21.07 20.74 20.40 20.67 20.21 21.14 20.94 20.74 NbO_(2.5) 6.906.96 7.02 6.30 6.38 6.22 6.26 6.29 SiO₂ 3.83 3.83 3.83 7.58 7.58 7.587.58 7.58 SrO TiO₂ 45.43 45.81 46.19 41.48 42.01 40.96 41.18 41.41YO_(1.5) 0.75 0.74 0.72 0.73 0.72 0.75 0.74 0.74 ZnO 0.58 0.58 0.58 0.530.53 0.52 0.52 0.52 ZrO₂ 4.60 4.64 4.68 4.20 4.25 4.15 4.17 4.19 WO₃TaO_(2.5) SbO_(2.5) AsO_(2.5) Cation 2.61 2.67 2.73 2.65 2.74 2.56 2.602.64 parameter B₂O₃ 5.40 5.39 5.38 6.57 6.55 6.59 6.58 6.57 [mol %] SiO₂[mol %] 4.80 4.79 4.78 9.55 9.52 9.58 9.57 9.55 SiO₂ + B₂O₃ 10.20 10.1810.16 16.12 16.07 16.17 16.15 16.12 [mol %] Properties T_(max) [° C.]1320 1320 1320 1320 1320 1300 1300 1300 n_(d) 2.180 2.182 2.184 2.1392.142 2.137 2.138 2.139 v_(d) 19.9 19.8 19.7 20.8 20.6 20.9 20.9 20.8Density 5.01 5.00 4.98 4.91 4.89 4.93 4.92 4.91 [g/cm³] n_(d) ²/Density0.949 0.953 0.957 0.932 0.938 0.927 0.929 0.931

TABLE 8 Cat % 57 58 59 60 61 62 63 64 AlO_(1.5) BO_(1.5) 10.43 8.80 8.808.80 8.80 10.43 10.43 8.80 BaO 4.98 5.05 5.01 4.96 4.91 5.08 5.03 4.99CaO GdO_(1.5) 3.04 3.08 3.05 3.03 3.00 3.10 3.07 3.05 KO_(0.5) LaO_(1.5)20.54 20.85 20.65 20.45 20.25 20.94 20.74 20.58 NbO_(2.5) 6.32 6.89 6.936.96 7.00 6.26 6.29 6.94 SiO₂ 7.58 4.02 4.02 4.02 4.02 7.58 7.58 4.02SrO TiO₂ 41.63 45.39 45.62 45.84 46.07 41.18 41.41 45.69 YO_(1.5) 0.730.74 0.73 0.73 0.72 0.74 0.74 0.73 ZnO 0.53 0.57 0.58 0.58 0.58 0.520.52 0.58 ZrO₂ 4.22 4.60 4.62 4.64 4.67 4.17 4.19 4.63 WO₃ TaO_(2.5)SbO_(2.5) AsO_(2.5) 0.01 0.01 Cation 2.67 2.65 2.68 2.72 2.76 2.60 2.642.70 parameter B₂O₃ 6.56 5.51 5.50 5.50 5.49 6.58 6.57 5.50 [mol %] SiO₂[mol %] 9.54 5.03 5.02 5.02 5.01 9.57 9.55 5.02 SiO₂ + B₂O₃ 16.10 10.5410.52 10.52 10.50 16.15 16.12 10.52 [mol %] Properties T_(max) [° C.]1300 1300 1300 1300 1300 1320 1320 1320 n_(d) 2.140 2.179 2.180 2.1812.182 2.139 2.139 2.180 v_(d) 20.7 19.9 19.8 19.8 19.7 20.9 20.8 19.8Density 4.91 4.99 4.99 4.98 4.97 4.92 4.91 4.99 [g/cm³] n_(d) ²/Density0.934 0.950 0.953 0.955 0.957 0.930 0.931 0.953

TABLE 9 Cat % 65 66 67 68 69 70 71 AlO_(1.5) BO_(1.5) 8.80 10.96 6.5810.43 10.43 10.43 10.43 BaO 5.46 4.93 5.05 5.16 5.16 5.16 5.20 CaOGdO_(1.5) 2.99 3.01 3.08 3.15 3.15 3.15 3.18 KO_(0.5) LaO_(1.5) 20.1920.35 20.82 21.27 21.27 21.27 21.47 NbO_(2.5) 6.94 6.86 7.02 11.36 6.125.17 6.10 SiO₂ 4.02 2.84 5.22 7.58 8.25 7.58 8.15 SrO TiO₂ 45.69 45.1746.22 35.64 40.29 40.81 40.64 YO_(1.5) 0.72 0.72 0.74 0.76 0.76 0.760.76 ZnO 0.58 0.57 0.59 0.52 0.51 0.52 ZrO₂ 4.63 4.57 4.68 4.13 4.084.13 4.06 WO₃ 1.03 TaO_(2.5) SbO_(2.5) AsO_(2.5) 0.01 0.01 0.01 Cation2.75 2.70 2.70 2.54 2.54 2.54 2.53 parameter B₂O₃ 5.48 6.94 4.07 6.816.59 6.55 6.60 [mol %] SiO₂ [mol %] 5.01 3.59 6.46 9.91 10.42 9.52 10.31SiO₂ + B₂O₃ 10.49 10.53 10.53 16.72 17.01 16.07 16.91 [mol %] PropertiesT_(max) [° C.] 1300 1320 1300 1300 1300 1310 1300 n_(d) 2.178 2.1792.181 2.132 2.130 2.133 2.132 v_(d) 19.8 19.8 19.8 21.3 21.1 20.8 21.4Density 4.98 4.98 4.99 4.97 4.92 4.92 4.94 [g/cm³] n_(d) ²/Density 0.9530.954 0.953 0.915 0.922 0.925 0.920

TABLE 10 Cat % 72 73 74 75 76 77 78 79 AlO_(1.5) BO_(1.5) 12.38 12.3812.38 12.38 16.18 12.21 12.03 11.85 BaO CaO GdO_(1.5) 4.52 4.56 4.604.64 4.46 4.62 4.69 4.76 KO_(0.5) LaO_(1.5) 25.69 25.93 26.16 26.3925.40 26.26 26.67 27.09 NbO_(2.5) 5.76 5.73 5.70 5.66 5.61 5.71 5.685.66 SiO₂ 8.44 8.44 8.44 8.44 6.25 8.36 8.27 8.18 SrO TiO₂ 37.94 37.7237.50 37.28 36.96 36.66 36.47 36.29 YO_(1.5) 0.93 0.94 0.95 0.96 0.920.95 0.97 0.98 ZnO 0.48 0.48 0.47 0.47 0.47 0.48 0.47 0.47 ZrO₂ 3.843.82 3.80 3.77 3.74 4.76 4.74 4.71 WO₃ TaO_(2.5) SbO_(2.5) AsO_(2.5)Cation 2.00 1.97 1.94 1.92 1.97 1.93 1.89 1.85 parameter B₂O₃ 8.22 8.238.24 8.26 10.97 8.12 8.02 7.92 [mol %] SiO₂ 11.20 11.22 11.24 11.26 8.4811.12 11.03 10.94 [mol %] SiO₂ + B₂O₃ 19.42 19.45 19.48 19.52 19.4519.24 19.05 18.86 [mol %] Properties T_(max) [° C.] 1300 1300 1300 13001300 1300 1300 1300 n_(d) 2.136 2.135 2.135 2.134 2.133 2.134 2.1352.134 v_(d) 21.6 21.6 21.7 21.8 21.6 21.9 21.8 21.6 Density 5.00 5.015.01 5.02 4.99 5.05 5.02 5.00 [g/cm³] n_(d) ²/Density 0.912 0.910 0.9100.907 0.912 0.902 0.908 0.911

TABLE 11 Cat % 80 81 82 83 84 85 86 87 AlO_(1.5) BO_(1.5) 11.68 11.8511.94 12.21 11.68 11.85 12.03 10.52 BaO 1.66 1.63 1.60 1.57 3.11 3.063.01 5.15 CaO GdO_(1.5) 4.58 4.50 4.42 4.33 4.06 3.99 3.92 3.92 KO_(0.5)LaO_(1.5) 26.05 25.58 25.13 24.65 23.07 22.70 22.33 22.32 NbO_(2.5) 4.544.57 4.60 4.62 4.73 4.75 4.78 4.81 SiO₂ 7.34 7.43 7.57 7.70 7.44 7.537.61 6.68 SrO TiO₂ 37.95 38.22 38.50 38.67 39.60 39.79 39.97 40.22YO_(1.5) 0.95 0.93 0.91 0.90 0.84 0.83 0.81 0.81 ZnO 0.48 0.48 0.48 0.490.50 0.50 0.50 0.51 ZrO₂ 4.77 4.81 4.84 4.86 4.98 5.00 5.03 5.06 WO₃TaO_(2.5) SbO_(2.5) AsO_(2.5) Cation 1.91 1.97 2.02 2.07 2.24 2.29 2.342.29 parameter B₂O₃ 7.67 7.77 7.81 7.96 7.50 7.60 7.71 6.67 [mol %] SiO₂9.65 9.74 9.89 10.05 9.56 9.66 9.75 8.48 [mol %] SiO₂ + B₂O₃ 17.32 17.5117.70 18.01 17.06 17.26 17.46 15.15 [mol %] Properties T_(max) [° C.]1320 1320 1300 1300 1300 1300 1300 1300 n_(d) 2.134 2.134 2.134 2.1342.134 2.134 2.134 2.134 v_(d) 21.9 21.8 21.7 21.6 21.4 21.4 21.3 21.4Density 5.07 5.04 5.03 5.00 4.98 4.96 4.94 5.00 [g/cm³] n_(d) ²/Density0.898 0.904 0.905 0.911 0.914 0.918 0.922 0.911

TABLE 12 Cat % 88 89 90 91 92 93 94 95 AlO_(1.5) BO_(1.5) 10.79 10.9611.14 11.23 11.68 12.65 9.71 11.85 BaO 5.07 4.99 4.91 4.83 3.11 3.005.02 4.82 CaO GdO_(1.5) 3.86 3.80 3.74 3.68 4.06 3.91 3.82 3.67 KO_(0.5)LaO_(1.5) 21.96 21.62 21.27 20.93 23.07 22.26 21.76 20.86 NbO_(2.5) 4.824.84 4.86 4.89 4.73 4.77 4.86 4.87 SiO₂ 6.81 6.90 6.99 7.13 7.44 7.177.71 6.77 SrO TiO₂ 40.31 40.50 40.69 40.89 39.60 39.92 40.70 40.76YO_(1.5) 0.80 0.79 0.77 0.76 0.84 0.81 0.79 0.76 ZnO 0.51 0.51 0.51 0.510.50 0.50 0.51 0.51 ZrO₂ 5.07 5.09 5.12 5.14 4.98 5.02 5.12 5.13 WO₃TaO_(2.5) SbO_(2.5) AsO_(2.5) 0.01 0.01 0.01 0.01 Cation 2.34 2.40 2.452.51 2.24 2.34 2.40 2.51 parameter B₂O₃ 6.84 6.94 7.04 7.09 7.50 8.136.10 7.50 [mol %] SiO₂ 8.63 8.73 8.83 8.99 9.56 9.21 9.69 8.57 [mol %]SiO₂ + B₂O₃ 15.47 15.67 15.87 16.08 17.06 17.34 15.79 16.07 [mol %]Properties T_(max) [° C.] 1300 1300 1300 1300 1300 1300 1300 1300 n_(d)2.134 2.134 2.134 2.134 2.133 2.134 2.134 2.134 v_(d) 21.4 21.3 21.221.1 21.4 21.2 21.3 21.1 Density 4.98 4.97 4.95 4.94 4.98 4.94 4.97 4.93[g/cm³] n_(d) ²/Density 0.914 0.916 0.920 0.922 0.914 0.922 0.916 0.924

TABLE 13 Cat % 96 97 98 99 AlO_(1.5) BO_(1.5) 12.73 12.38 12.21 11.83BaO 4.77 CaO GdO_(1.5) 4.47 4.52 4.44 3.63 KO_(0.5) LaO_(1.5) 25.4125.69 25.25 20.78 NbO_(2.5) 5.74 5.76 5.79 4.82 SiO₂ 8.61 8.44 8.92 6.37SrO TiO₂ 37.80 37.94 38.13 41.60 YO_(1.5) 0.92 0.93 0.92 0.77 ZnO 0.480.48 0.48 0.53 ZrO₂ 3.83 3.84 3.86 4.89 WO₃ TaO_(2.5) SbO_(2.5)AsO_(2.5) 0.008 Cation 2.02 2.00 2.05 2.12 parameter B₂O₃ 8.45 8.22 8.067.49 [mol %] SiO₂ 11.43 11.20 11.78 8.07 [mol %] SiO₂ + B₂O₃ 19.88 19.4219.84 15.56 [mol %] Properties T_(max) [°C] 1320 1300 1320 1280 n_(d)2.134 2.136 2.135 2.134 ν_(d) 21.6 21.6 21.5 21.3 Density 4.98 5.00 4.974.95 [g/cm³] n_(d) ²/Density 0.914 0.912 0.917 0.920

TABLE 14 Cat % A B C D E F G AlO_(1.5) BO_(1.5) 6.57 11.88 7.69 10.43BaO 10.71 14.82 8.44 3.84 4.54 10.34 5.04 CaO GdO_(1.5) 4.00 2.87 2.573.08 KO_(0.5) LaO_(1.5) 15.29 21.18 22.56 19.62 20.09 17.14 20.81NbO_(2.5) 5.54 4.64 5.09 9.61 6.71 6.62 21.98 SiO₂ 12.50 12.50 12.5013.42 4.75 6.25 7.58 SrO TiO₂ 52.28 43.78 48.03 38.13 44.70 44.15 25.64YO_(1.5) 0.82 0.74 ZnO 0.52 ZrO₂ 3.69 3.09 3.39 4.81 4.47 4.42 4.19 WO₃TaO_(2.5) SbO_(2.5) AsO_(2.5) Cation 4.84 3.02 3.06 2.93 2.90 3.18 2.62parameter B₂O₃ 4.10 7.49 4.66 7.29 [mol %] SiO₂ [mol %] 13.95 14.3514.51 16.75 6.00 7.57 10.61 SiO₂ + B₂O₃ 13.95 14.35 14.51 20.85 13.4912.23 17.90 [mol %] Properties T_(max) [° C.] 1370 1450 1350 1390 13801360 1350 n_(d) 2.154 2.107 2.149 2.121 2.166 2.142 2.125 v_(d) 19.321.6 20.4 21.0 19.8 20.4 21.7 Density 4.70 4.95 4.91 4.84 4.90 4.90 5.03[g/cm³] n_(d) ²/Density 0.987 0.897 0.940 0.930 0.958 0.937 0.897

FIGURES

FIG. 1 shows an internal transmission spectrum of exemplary glass 31from Table 1. It can be seen that this example exhibits at 460 nm aninternal transmission T_(i) of more than 88% at a sample thickness of 10mm. In addition, the transmission curve shows the advantageously steepfall from the visible region of the spectrum to the adjoining UV region.

FIG. 2 shows the relationship of the cation parameter K and T_(max) forexemplary embodiments and comparative examples from Tables 1 to 9 and14. It can be seen that the glasses provided according to the inventionfrom Tables 1 to 9 have a cation parameter in the range from above 2.0and max. 2.8 and at the same time a T_(max) of in this case less than1330° C., i.e. they have a relatively low liquidus temperature. Inaddition, all examples have a refractive index n_(d) of more than 2.10.Thus, what has been found in the context of the invention is a stableglassy range alongside a low liquidus temperature in ahigh-refractive-index glass system.

FIG. 3 shows the relationship of the cation parameter K and T_(max) forexemplary embodiments and comparative examples from the tables. Inaddition to the exemplary embodiments shown in FIG. 2 , the exemplaryembodiments of Tables 10 to 12 are depicted. It can be seen that evenexamples having a cation parameter in the range from above 1.8 to 2.0alongside a refractive index of more than 2.10 may at the same time havea T_(max) here of less than 1330° C., i.e. they may have a relativelylow liquidus temperature.

In the context of the invention, it was found that glasses having acation parameter of more than 2.0 have a lower tendency tocrystallization than glasses having a cation parameter of max. 2.0,which have a stronger tendency to crystallization. A higher tendency tocrystallization narrows the process window during production, makingproduction more laborious for such glasses. In the process window thetemperature of the melt is above T_(max). However, in order that theviscosity is not too low and for it to still be possible for the glassto be handled, for example with regard to hot forming, the chosentemperature cannot be too high. A further consequence of an increasedtendency to crystallization may be, for example, that it is possible toproduce only smaller glass articles.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

What is claimed is:
 1. An optical glass having a refractive index n_(d)of more than 2.10 and comprising at least TiO₂, NbO_(2.5), LaO_(1.5),SiO₂, and B₂O₃, the glass having the following features: a cationparameter K of 1.8<K≤2.8, wherein K=(Ti-eq.+SiO₂+(BO_(1.5))/2)/(La-eq.),the molar fractions of Ti-eq., SiO₂, BO_(1.5) and La-eq. in the cationparameter K being in cat %; a sum total of glass components SiO₂ andB₂O₃ of 8.0 mol %≤(SiO₂+B₂O₃)≤20.0 mol %, the proportion of B₂O₃being >0 mol % and the proportion of SiO₂>0 mol %; and a temperatureT_(max)≤1330° C.
 2. The optical glass of claim 1, having an internaltransmission τ_(i) of at least 75% measured at a wavelength of 460 nmand a sample thickness of 10 mm.
 3. The optical glass of claim 2,wherein the internal transmission is τ_(i) at least 90%.
 4. The opticalglass of claim 1, having a density of <5.3 g/cm³ and/or a numericalvalue for a ratio (n_(d))²/density of more than 0.85.
 5. The opticalglass of claim 1, wherein the proportion of the components TiO₂ andLaO_(1.5) in the glass is at least 53.0 cat %.
 6. The optical glass ofclaim 5, wherein the proportion of NbO_(2.5) is at least 7.0 cat %. 7.The optical glass of claim 1, wherein the proportion of the componentsTiO₂, LaO_(1.5) and NbO_(2.5) is at least 60.0 cat %.
 8. The opticalglass of claim 1, having at least one of the following features: aproportion of Ti-eq. of at least 43.0 cat % and/or not more than 63.0cat %; a proportion of La-eq. of at least 21.0 cat % and/or not morethan 35.0 cat %; or a sum total (Ti-eq.+La-eq.) of at least 72.0 cat %and/or not more than 85.0 cat %.
 9. The optical glass of claim 8,wherein the proportion of La-eq. is not more than 30.0 cat % and/orwherein the proportion of Ti-eq. is at least 45.0 cat %.
 10. The opticalglass of claim 1, wherein the cation parameter is at least 1.9.
 11. Theoptical glass of claim 10, wherein the cation parameter is at least 2.2.12. The optical glass of claim 1, comprising the following components incat %: SiO₂   >0 to <20.0; BO_(1.5)   >0 to <20.0; TiO₂ 32.0 to 52.0;NbO_(2.5)  3.0 to 15.0; ZrO₂   0 to 11.0; WO₃   0 to 5.0; TaO_(2.5)   0to 5.0; AlO_(1.5)   0 to 5.0; SbO_(2.5)   0 to 0.5; AsO_(2.5)   0 to0.5; LaO_(1.5) 13.0 to 30.0; GdO_(1.5)   0 to 10.0; YO_(1.5) 0 to 5.0;and YbO_(1.5)   0 to 5.0.


13. The optical glass of claim 1, comprising the following components incat %: SiO₂   >0 to <20.0; BO_(1.5)   >0 to <20.0; TiO₂ 32.0 to 52.0;NbO_(2.5)  4.0 to 15.0; ZrO₂   0 to 11.0; WO₃   0 to 5.0; TaO_(2.5)   0to 5.0; AlO_(1.5)   0 to 5.0; SbO_(2.5)   0 to 0.5; AsO_(2.5)   0 to0.5; LaO_(1.5) 13.0 to 28.0; GdO_(1.5)   0 to 10.0; YO_(1.5) 0 to 5.0;and YbO_(1.5)   0 to 5.0.


14. The optical glass of claim 1, comprising the following components incat %: SiO₂  2.0 to 14.0; BO_(1.5)  1.0 to 18.0; TiO₂ 34.0 to 50.0;NbO_(2.5)  5.0 to 13.0; ZrO₂ 2.0 to 8.0; WO₃   0 to 2.0; TaO_(2.5)   0to 1.0; AlO_(1.5)   0 to 2.0; SbO_(2.5)   0 to 0.1; AsO_(2.5)   0 to0.1; LaO_(1.5) 16.0 to 24.0; GdO_(1.5) 2.0 to 8.0; YO_(1.5) 0.3 to 2.0;and BaO   0 to 6.5.


15. The optical glass of claim 1, having a content of BaO of not morethan 6.5 cat % and/or a content of TiO₂ of at least 39 cat %.
 16. Theoptical glass of claim 1, having an Abbe number (ν_(d)) of more than18.5 and/or less than 30.0.
 17. The optical glass of claim 16, whereinthe Abbe number is more than 18.9 and/or less than 25.0.
 18. The opticalglass of claim 1, wherein the glass, based on the respective cations, isessentially free of one or more constituents selected from groupconsisting of bismuth, lead, germanium, phosphate, lithium, magnesium,cadmium, gallium, coloring components, cobalt, vanadium, chromium,molybdenum, copper, nickel, and combinations thereof.
 19. A glassarticle, comprising: an optical glass having a refractive index n_(d) ofmore than 2.10 and comprising at least TiO₂, NbO_(2.5), LaO_(1.5), SiO₂,and B₂O₃, the glass having the following features: a cation parameter Kof 1.8<K≤2.8, wherein K=(Ti-eq.+SiO₂+(BO_(1.5))/2)/(La-eq.), the molarfractions of Ti-eq., SiO₂, BO_(1.5) and La-eq. in the cation parameter Kbeing in cat %; a sum total of glass components SiO₂ and B₂O₃ of 8.0 mol%≤(SiO₂+B₂O₃)≤20.0 mol %, the proportion of B₂O₃ being >0 mol % and theproportion of SiO₂>0 mol %; and a temperature T_(max)≤1330° C.; whereinthe glass article is in the form of a glass substrate, a wafer, a lens,a spherical lens, a prism, an asphere, an optical waveguide, a fibre,and/or a plate.